JP7369542B2 - Method and device for reverse separation of aromatic compounds - Google Patents

Description

The present invention falls within the field of methods and devices for the separation of aromatic compounds. The object according to the invention applies in particular in the case of aromatic complexes requiring distillative separation between benzene, toluene and heavier compounds with more than 8 carbon atoms (hereinafter designated as C8+ compounds). .

DE 10 2005 201 2 describes a method which allows an overall energy saving in terms of fuel and power consumption of an aromatics complex for the distillative separation between benzene, toluene and C8+ compounds. In particular, the principle of the method consists in the generation of low-pressure steam in a given column, the low-pressure steam thus generated being used as a heat exchange fluid to carry out intermediate compression, e.g. with or without reboiling at a lower temperature in the other column.

French Patent Invention No. 2998301

(overview)
In the above background, the first object of the invention is to make it possible to reduce the amount of energy required to carry out the separation between benzene, toluene and C8+ compounds.

According to a first aspect, the above object and further advantages are a method for separating in a separation device a feedstock comprising benzene, toluene and a compound containing 8 or more carbon atoms, comprising: The separation device comprises at least one reformate column, at least one aromatics extraction unit and at least one transalkylation unit, and the effluent from said units is transferred to a distillation column: a benzene column. , separated in toluene column and stabilization column, following steps:
The toluene column is directly fed with the C7+ fraction originating from the bottom of the stabilization column located downstream of the transalkylation unit, and the top product from the toluene column rich in benzene and toluene is combined with the top product from the toluene column rich in benzene and toluene. withdrawing the bottom product from the toluene column enriched with compounds having more than 1 carbon atoms;
feeding a top product from the toluene column to a benzene column and withdrawing a benzene-rich top product from the benzene column and a toluene-rich bottom product from the benzene column; feeding the toluene-enriched bottom product from the benzene column to an alkylation unit;
The toluene column is fed with an essentially aromatic fraction originating from the aromatics extraction unit, and the toluene column feed originating from the aromatics extraction unit is fed with toluene originating from the bottom of the stabilization column. Separately from and above the column feed, or the essentially aromatic fraction originating from the aromatics extraction unit is fed into the benzene column in a mixture with the top product from the toluene column. or by a method of feeding separately.

According to one or more embodiments, the toluene column is further fed with the top product from the purification column, either as a mixture with the C7+ cut from the bottom of the stabilization column or separately.

According to one or more embodiments, the transalkylation unit is further fed with the top product from the purification column, either as a mixture with the bottom product from the benzene column or separately.

According to one or more embodiments, the separation device further comprises a para-xylene separation unit and a xylenes isomerization unit, and the effluent is separated in the following additional distillation columns: a xylenes column, a heavy aromatics columns, raffinate columns, extract columns, purification columns, deheptanizers and strippers.

According to one or more embodiments, only the xylenes column and the heavy aromatics column feed C9+ aromatics to the transalkylation unit.

According to one or more embodiments, the reformate column is fed with a feedstock to produce a C7-cut at the top of the reformate column, and the aromatics extraction unit is fed with a C7-cut. The paraffinic compounds are extracted from the C7 fraction to produce an essentially aromatic fraction.

According to one or more embodiments, the operating conditions for the benzene column are as follows:
Temperature: 130°C to 180°C in the reboiler, 70°C to 130°C in the condenser;
Pressure: 0.1 MPa to 0.5 MPa; and theoretical plate: 35 to 55 plates.

According to one or more embodiments, the operating conditions for the toluene column are as follows:
Temperature: 130°C to 260°C in the reboiler, 50°C to 200°C in the condenser;
Pressure: 0.05 MPa to 1 MPa; and theoretical plate: 30 to 55 plates.

According to a second aspect, the above objects, and further advantages, provide a device for the separation of feedstocks containing benzene, toluene and compounds having 8 or more carbon atoms, comprising at least one reformate a column, at least one aromatics extraction unit and at least one transalkylation unit, the following columns for the distillation of the effluent from said unit: a benzene column, a toluene column and a stabilization column. further including;
- the toluene column is fed with the C7+ fraction originating from the bottom of the stabilization column located downstream of the transalkylation unit and is fed with the top product from the toluene column enriched in benzene and toluene and more than 8 suitable for delivering the bottom product from a toluene column enriched with compounds having carbon atoms of;
- the benzene column is fed with the top product from the toluene column and is suitable for delivering the benzene-rich top product from the benzene column and the toluene-rich bottom product from the benzene column; and
- the transalkylation unit is suitable for treating the toluene-rich bottom product from the benzene column;
The toluene column is suitable for feeding the essentially aromatic fraction originating from the aromatics extraction unit, and the toluene column feed originating from the aromatics extraction unit is fed to the stabilization column. The benzene column is carried out separately from the toluene column feed originating from the bottom of the toluene column, or the benzene column feeds the essentially aromatic fraction originating from the aromatics extraction unit to the top production from the toluene column. or by means of a device suitable for delivery as a mixture with other substances or separately.

According to one or more embodiments, the toluene column is suitable for feeding the top product from the purification column as a mixture with or separately from the C7+ fraction originating from the bottom of the stabilization column. There is.

According to one or more embodiments, the transalkylation unit is suitable for feeding the top product from the purification column as a mixture with the bottom product from the benzene column or separately.

According to one or more embodiments, the separation device comprises a para-xylene separation unit, a xylenes isomerization unit and the following additional columns for distillation of said effluent: xylenes column, heavy aromatics column. , a raffinate column, an extract column, a purification column, a deheptanization column, and a stripper.

According to one or more embodiments, the separation device feeds the feed to the reformate column to produce a C7-fraction at the top of the reformate column and provides a C7-fraction to the aromatics extraction unit. is suitable for extracting paraffinic compounds from the C7 fraction and producing an essentially aromatic fraction.

According to one or more embodiments, the operating conditions for the benzene column are as follows:
Temperature: 130°C to 180°C in the reboiler, 70°C to 130°C in the condenser;
Pressure: 0.1 MPa to 0.5 MPa; and theoretical plate: 35 to 55 plates.

According to one or more embodiments, the operating conditions for the toluene column are as follows:
Temperature: 130°C to 260°C in the reboiler, 50°C to 200°C in the condenser;
Pressure: 0.05 MPa to 1 MPa; and theoretical plate: 30 to 55 plates.

Embodiments of the method and device referred to above, as well as other features and advantages, will become apparent upon reading the description that will follow. However, reference is made to the following drawings, which are given by way of illustration only and not as a limitation.

FIG. 1 describes a diagram of an aromatics complex containing a reference separation section (F) for the separation of benzene, toluene and C8+ compounds. FIG. 2 describes a diagram of an aromatics complex comprising a separation section (F) according to the invention for the separation of benzene, toluene and C8+ compounds.

(detailed explanation)
The present invention relates to the field of methods and devices for the separation of feedstocks containing benzene, toluene and C8+ (eg C8-C10) compounds, particularly those which may contain para-xylene.

The separation method and device according to the present invention comprises a series of conversion and separation steps and sections for separating aromatic compounds ranging from benzene to aromatic compounds having more than 10 carbon atoms (designated C10+ compounds). Starting from a rich feedstock, for example originating from a catalytic reforming unit, the benzene/toluene/xylenes are separated and/or the toluene is converted into C8+ compounds, in particular those known as xylenes 8 can be defined as an aromatic compound having 5 carbon atoms, more specifically intended to be converted to para-xylene. Aromatics-rich feedstocks typically contain sulfur-containing, nitrogenous, and olefinic compounds at concentrations ranging from very low to zero (e.g., sulfur content <0.5 ppm by weight and or nitrogen content <0.5 ppm by weight and/or bromine number <1 g/100 g according to ASTM D1159). This is because these compounds can affect the performance quality and service life of a given catalyst and molecular sieve employed in a unit of an aromatics complex.

The first objective according to the invention is defined as the reversal of the order of the benzene column and the toluene column combined with the separate feeding of the column feedstock (directed as a mixture to the benzene column according to patent FR 2 998 301 B1). This is done for better energy efficiency.

In the description that follows, the term "complex" is used to denote any refining and petrochemical device comprising at least two distillation columns. This definition is very broad and includes, for example, devices for the catalytic cracking of gasoline and devices for the production of para- or meta-xylene from aromatic fractions, and includes "aromatic complexes" known as. Although the description that follows and the examples illustrating the separation method and device according to the invention are given in the case of aromatics complexes, aromatics complexes constitute the only situation of application and are presented in the description of the invention. It is clearly understood that the invention is in no way limiting the scope of the separation methods and devices used.

FIG. 1 describes a reference method and a diagram of the aromatics complex for the separation of benzene, toluene and C8+ compounds.

Specifically described in connection with FIG. 1 is an arrangement of two columns, a benzene column (C9) and a toluene column (C10). This arrangement of columns separates the essentially aromatic C6-C7 fraction originating from the aromatics extraction unit (P1) and the stabilization column (C11) downstream of the transalkylation unit (P4). A mixture with the C7+ fraction originating from the bottom is fed. The benzene column (C9) produces benzene as the final product at the top and a C7+ fraction at the bottom, which is sent to the toluene column (C10). Toluene is recovered at the top of the toluene column (C10), while the C8+ fraction is extracted at the bottom of the toluene column (C10).

FIG. 2 provides a diagram of a method and device for separation according to one or more embodiments of the present invention, in which the energy consumption required for the separation between benzene, toluene and C8+ compounds is compared to the reference It is particularly possible to reduce compared to methods and aromatic complexes.

In connection with FIG. 2, it is specifically noted that the toluene column (C10) feeds the C7+ fraction originating from the bottom of the stabilization column (C11) located downstream of the transalkylation unit (P4). modified to withdraw the top product from the toluene column (C10) enriched in benzene and toluene and the bottom product from the toluene column (C10) enriched in compounds with 8 or more carbon atoms. The benzene column (C9) is fed with the top product from the toluene column (C10) and the benzene-rich top product from the benzene column (C9). and the toluene-rich bottom product from the benzene column (C9); the transalkylation unit (P4) is fed with the toluene-rich bottom product from the benzene column (C9). According to one or more embodiments, the toluene column (C10) also contains an essentially aromatic fraction (denoted below as C6-C7 fraction) originating from the aromatics extraction unit (P1). The feed of the toluene column (C10) originating from the aromatics extraction unit (P1) is separate from the feed of the toluene column (C10) originating from the bottom of the stabilization column (C11) and its upper part. (downstream). According to one or more embodiments, the benzene column (C9) also carries the C6-C7 fraction originating from the aromatics extraction unit (P1) as a mixture with the top product from the toluene column (C10) or It will be shipped separately.

The conversion and separation steps and sections of the separation method and device according to the invention are described in more detail below.

If the purpose is only to separate benzene and C8 compounds and optionally toluene from the feedstock, only stages or sections C1, P1, C9, C10, P4 and C11 are presented. The other sections below are of use only when it is desired to separate xylenes, and indeed to maximize the yield of para-xylene.

(Reformate tower (C1))
The feedstock to be treated is sent via line (1) to the first distillation column. This distillation column is designated as a reformate column (C1), which converts toluene and lighter compounds (a fraction of C7- compounds) into compounds heavier than toluene (a fraction of C8 to C10+ compounds). Separate from.

(Aromatic compound extraction unit (P1))
The top effluent from the reformate column (C1) is directed via line (10) to the aromatics extraction unit (P1).

The toluene and optionally the compounds recovered at the bottom of the stripper (C8) are sent via line (81) to the aromatics extraction unit (P1).

The aromatics extraction unit (P1) separates an essentially aromatic C6-C7 fraction from a product containing paraffinic compounds, which is passed through line (13). sent to the outside of the aromatics complex via The solvent preferably used in the aromatic compound extraction unit (P1) is N-formylmorpholine (NFM).

In connection with FIG. 1, the C6-C7 fraction originating from the aromatics extraction unit (P1) is directed via line (12) to the benzene column (C9) in the separation section (F).

In connection with FIG. 2, the C6-C7 fraction originating from the aromatics extraction unit (P1) is transferred in the separation section (F) via line (12) to the benzene column (C9) or containing to a toluene column (C10) to be purified from any C8 compounds that may be present.

According to one or more embodiments, the aromatics extraction unit (P1) includes an extractive distillation unit.

(Xylene tower (C2))
The C8-C10+ aromatics recovered at the bottom of the column (C1) are sent via line (11) to the xylenes column (C2), where the C9 and heavier aromatics (of the C9+ compounds) are Compounds are separated from the xylenes fraction containing C8 aromatics. This xylenes fraction is fed to the aromatics complex unit located downstream.

(Paraxylene separation unit (P2))
The xylenes fraction, i.e. the C8 aromatics fraction containing para-xylene, meta-xylene, ortho-xylene and ethylbenzene, is collected at the top of the xylenes column (C2) and sent via line (20) to para-xylene. The para-xylene separation unit (P2) selectively recovers para-xylene present in the xylene fraction.

Said para-xylene separation unit (P2) may be a para-xylene adsorption unit, which for example contains a mixture of para-xylene and a desorbent (known as extract) and other C8-aromatic compounds and (as raffinate). known) is suitable for producing mixtures of desorbents.

The adsorbent used is a molecular sieve dedicated to the adsorption of paraxylene. That is, it exhibits a particularly high affinity for this compound.

Commonly used adsorbent solids are faujasite type zeolites shaped by siliceous binders, which have been exchanged with barium or potassium. A preferably used desorbent is para-diethylbenzene (PDEB).

According to one or more embodiments, the paraxylene separation unit (P2) comprises a paraxylene crystallization unit, for example as described in patent US 3 467 724.

According to one or more embodiments, the para-xylene separation unit (P2) comprises a combination of a para-xylene adsorption unit and a crystallization unit, for example as described in patent EP-B-053 191 It's something like this.

(Extract tower (C5))
This column is used when the separation unit is of the para-xylene adsorption type. The extract stream originating from the para-xylene adsorption unit and containing para-xylene and desorbent is sent via line (22) to the extract column (C5), which extract column (C5) Separate the xylene from the desorbent. The desorbent recovered at the bottom of the extract column (C5) is sent back to the adsorption column via line (51). The para-xylene recovered at the top of the extract column (C5) is sent to the purification column (C6).

(Purification tower (C6))
The top stream from the extract column (C5) is sent via line (50) to the purification column (C6). The purification column (C6) separates toluene (which is partially extracted together with para-xylene) from para-xylene.

The resulting high purity para-xylene is recovered at the bottom of the purification column (C6) and conveyed as final product by pumping for storage via line (61).

According to one or more embodiments, the top product from the purification column (C6) is directed (line 60) to the benzene column (C9) in the separation section (F).

In connection with FIG. 2, the top product from the purification column (C6) is sent to the benzene column (C9) as a mixture with the top stream from the column (C10) or via a separate feed, or toluene. The top product is directed to the column (C10), for example as a mixture with the C7+ fraction originating from the bottom (line (112)) of the stabilization column (C11), from the predetermined C8 compounds it may contain. It can be purified; and/or recycled directly to the transalkylation unit (P4), for example as a mixture with the C7+ fraction extracted at the bottom of the benzene column (C9).

(Raffinate tower (C4))
The raffinate originating from the paraxylene separation unit (P2) is sent via line (23) to the raffinate column (C4). The raffinate column (C4) separates the C8 aromatics (raffinate) from the desorbent. The desorbent recovered at the bottom of the column (C4) is sent back to the para-xylene adsorption section (P2) via line (41).

The raffinate (C8 aromatics fraction) is extracted by side sink and sent via line (40) as feed to the xylenes isomerization unit (P3).

(Desorbent tower (not shown))
This column is used when the para-xylene separation unit is of the para-xylene adsorption type. A small portion of the desorbent flowing into the para-xylene adsorption unit is sent to a desorbent column (not shown) from which heavy compounds that would otherwise accumulate in the loop are removed.

(Xylene isomerization unit (P3))
The xylenes isomerization unit (P3) is used to convert the para-xylene-depleted feedstock into a stream of xylenes in thermodynamic equilibrium (denoted as "isomerates").

All types of catalysts capable of isomerizing hydrocarbons having 8 carbon atoms can be used in the separation methods and devices according to the invention. Dehydrogenating metals, such as platinum, palladium or nickel, and acid phases, such as doped alumina, zeolites, such as mordenite, MFI, zeolite Y, or zeolite or non-zeolite molecular sieves with acidity, such as aluminoline. Catalysts containing acid salts (eg, aluminophosphates (AlPO), silicoaluminophosphates (SAPO)) are preferably used. More preferably therefore zeolites of the EUO structure type, such as zeolite EUI, zeolite ZSM50 or zeolite TPZ3, as described in patents US 4 640 829, EP-B-042 226 or EP-B-051 318 It is possible to use an isomerization catalyst containing.

(Deheptanizer (C7))
The effluent from the xylenes isomerization unit (P3) is sent via line (42) to the deheptanizer (C7), which converts isomers (C8+ aromatics) to C7 -Separated from light fraction. This C7-light fraction is recovered at the top of the deheptanizer (C7). This C7 fraction is sent via line (71) to a stripper (C8), where light compounds are separated from the C7 fraction.

The C8+ fraction is formed from xylenes and heavier compounds and is recovered at the bottom of the deheptanizer (C7) and is sent via line (72) to the xylenes column (C2). Recirculated.

In view of the significant content of light (C4-) compounds in the deheptanizer (C7), the top product from the deheptanizer (C7) is a vapor (consisting mainly of light (C4-) compounds). It may include a phase (70) and a liquid phase (71), both originating from a reflux drum (not shown).

(Stripper (C8))
The stripper (or stripping column) (C8) is fed via the top of the deheptanizer (C7).

The stabilized C7-fraction is collected at the bottom of the stripper (C8) and sent via line (81) to the aromatics extraction unit (P1).

Light (C4-) compounds originating from the top of the stripper are mixed with light compounds from the top of the deheptanizer (line (70)) and removed via line (80).

(Heavy aromatic compound column (C3))
The C9+ aromatics recovered at the bottom of the xylenes column (C2) are sent to the heavy aromatics column (C3) via the line (21), and the heavy aromatics column (C3) C9 and C10 aromatics are separated from heavier compounds (eg naphthalene). This heavier compound may have an undesirable effect on the transalkylation catalyst and is recovered at the bottom via line (31).

(Transalkylation unit (P4))
The C9 and C10 aromatics recovered at the top of the heavy aromatics column (C3) are sent via line (30) to the transalkylation unit (P4).

With reference to FIG. 1, the C9 and C10 aromatics are mixed with toluene originating from the top of the toluene column (C10).

With reference to Figure 2, the C9 and C10 aromatics are mixed with toluene originating from the bottom of the benzene column (C9).

The transalkylation unit (P4) is a C9+ aromatic compound and xylenes isomerization unit (P3) originating from the toluene and reformate column (C1) (the xylenes column (C2) and the heavy aromatic compound column (C3)). The C9+ aromatics originating from the isomerate (after passing through ) are converted into a mixture of xylenes and benzene via a thermodynamically limited reaction. According to one or more embodiments, the xylenes column (C2) and the heavy aromatics column (C3) carry the majority (substantially all) of the C9+ aromatics sent to the transalkylation unit (P4). )I will provide a.

All types of transalkylation catalysts can be used in the separation methods and devices according to the invention, for example mordenite- or faujasite-based catalysts as described in patent US 3 437 710 or as described in patent US 5 030 787. or catalysts based on mordenite and MFI zeolites as described in patent application US 2012/0065446. These catalysts generally further comprise a metal compound, preferably selected from the group formed by rhenium, nickel, cobalt, molybdenum, tungsten, palladium and platinum.

(Stabilization tower (C11))
The effluent from the transalkylation unit (P4) contains benzene, unconverted toluene and C8 (e.g. xylenes) and C9+ aromatics, which is passed through line (102) to It is sent to the stabilization tower (C11). The stabilization column (C11) separates compounds lighter than benzene from benzene and heavier aromatic compounds (denoted as C7+ compounds).

The gas leaving the stabilization column (C11) (reflux drum) is sent via line (110) to the boundary of the aromatics complex.

The unpurified benzene fraction is taken off as a side stream and sent via line (111) to the stripping column (C8). A stripping column (C8) makes it possible to separate light compounds from said fraction.

According to one or more embodiments, partial condensation of the top gas from the stabilization column (C11) is obtained by a cooling tower and optionally a subsequent water cooler.

(Separation section (F))
Separation section (F) includes a benzene column (C9) and a toluene column (C10).

(Benzene tower (C9) by reference method and aromatics complex)
In connection with FIG. 1, the C6-C7 fraction (line (12)) originating from the aromatics extraction unit (P1) is different from the C7+ fraction (line (112)) originating from the bottom of the stabilization column (C11). ) and sent to the benzene tower (C9). From the benzene column (C9), benzene is extracted at the top as final product via line (90). The C7+ fraction extracted at the bottom of the benzene column (C9) is directed via line (91) to the toluene column (C10).

(Toluene column (C10) by reference method and aromatics complex)
In connection with FIG. 1, the toluene column (C10) is fed with the C7+ fraction originating from the bottom of the benzene column (C9). The toluene recovered at the top of the toluene column (C10) is directed via line (100) as feed to the transalkylation unit (P4). The C8+ fraction extracted at the bottom of the column (C10) is recycled to the xylenes column (C2) via line (101).

(Toluene column (C10) using the separation method and device according to the present invention)
In connection with FIG. 2, the toluene column (C10) is fed with the C7+ fraction (line (112)) originating from the bottom of the stabilization column (C11). The top product from the toluene column (C10) is a fraction enriched in C7-compounds (e.g. substantially toluene + C6-compounds), and the bottom product is a fraction enriched with C7-compounds (e.g. essentially toluene + C6-compounds), and the bottom product is aromatic compounds with 8 carbon atoms. It is a C8+ fraction rich in

The C8+ fraction extracted at the bottom of the toluene column (C10) (i.e. the bottom product from the toluene column (C10) enriched in compounds with 8 or more carbon atoms) is fed via line (101). , is recycled to the xylenes column (C2). The xylenes column (C2) separates C9+ and heavier compounds from the C8 aromatics fraction, which is fed to the para-xylene separation device.

According to one or more embodiments, the C6-C7 fraction originating from the aromatics extraction unit (P1) is transferred to the toluene column (C10) along with the C7+ fraction originating from the bottom of the stabilization column (C11). Sent separately from and in addition to feeding.

Since the effluent originating from the top of the purification column (C6) may have a very low flow rate compared to the other two streams treated by the separation section (F), one or more of the According to an embodiment, said effluent is mixed with a C7+ fraction originating from the bottom of the column (C11). Any other position is possible for feeding the stream originating from the top of the purification column (C6) to the separation section (F). For example, the top of the purification column (C6) can be recycled to the benzene column (C9) or directly to the transalkylation unit (P4). For example, it is possible to feed the transalkylation unit (P4) with a mixture comprising the bottom product from the benzene column (C9) and the top product from the purification column (C6).

According to one or more embodiments, the operating conditions for the toluene column are as follows:
Temperature: 130°C to 260°C in the reboiler, 50°C to 200°C in the condenser;
Pressure: 0.05 MPa to 1 MPa; and theoretical plate: as per 30 to 55 plates.

(Benzene tower (C9) using the separation method and device according to the present invention)
In connection with FIG. 2, the C7-cut extracted at the top of the toluene column (C10) (i.e. the top product from the toluene column enriched in benzene and toluene) is transferred via line (91) to Directed to the benzene tower (C9).

According to one or more embodiments of the invention, for example, if the C6-C7 fraction originating from the aromatics extraction unit (P1) contains only minimal amounts of C8+ (e.g. the C6-C7 fraction C8+ <1 wt%, preferably <0.5 wt%, even more preferably <0.3 wt%) in the C6-C7 fraction originating from the aromatics extraction unit (P1) (toluene (either as a mixture with the top of the column (C10) or separately) to the benzene column (C9) downstream of the toluene column (C10). According to one or more embodiments, the feed of the benzene column (C9) originating from the aromatics extraction unit (P1) is preferably separate from the feed originating from the top of the toluene column (C10). It is done higher up (downstream).

Starting from the benzene column (C9), the benzene-rich top product is extracted as final product via line (90). According to one or more embodiments, the benzene-rich product is extracted by side sink. According to one or more embodiments, light and non-condensable compounds are removed via a vapor stream at the top of the column (line (92)). The toluene-rich bottom product from the benzene column (C9) is directed via line (100) to the transalkylation unit (P4).

According to one or more embodiments, the operating conditions for the benzene tower are as follows:
Temperature: 130°C to 180°C in the reboiler, 70°C to 130°C in the condenser;
Pressure: 0.1 MPa to 0.5 MPa; and Theoretical plate: As per 35 to 55 stages.

In Figures 1 and 2, for reasons of simplicity, no reflux section, reflux drum or condenser is shown; any known condensation means (eg: cooling tower and/or water cooler) may be used.

(Example)
In the example, the separation section (F) separates two feedstocks:
- feedstock (1): the C6-C7 fraction originating from the aromatic compound extraction unit (P1); and - feedstock (2): the C7+ fraction originating from the bottom of the stabilization column (C11) fed. Ru.

In the example, the top of the purification column (C6) is recycled directly to the transalkylation unit (P4).

(Example 1)
The compositions of the two feedstocks of the separation section (F) (Feedstock (1) and Feedstock (2)) are shown in Table 1.

The fraction leaving separation section (F) is a product rich in benzene, toluene and C8+ compounds, respectively, according to the composition in Table 2.

The composition of four fractions is evaluated:
- Configuration (1) (corresponds to the reference separation method and device): the benzene column is fed with a mixture of two feedstocks. The bottom of the benzene column is fed to the toluene column.
- Configuration (2) (comparison): The benzene column is fed with two feedstocks, which are introduced into the column separately. The bottom of the benzene column is fed to the toluene column.
- Configuration (3) (comparison): The toluene column is fed with a mixture of two feedstocks. The top of the toluene column is fed to the benzene column.
- Configuration (4) (according to the method and device of separation according to the invention): The toluene column is fed with two feedstocks, which are introduced into the column separately. Feedstock (1) is fed above feedstock (2). The top of the toluene column is fed to the benzene column.

The location of the feed is optimized in each of the configurations to minimize the energy consumption of each reboiling of the columns.

The geometry and energy consumption of each of the configurations are shown in Table 3.

Surprisingly, only by reversing the order of the columns and introducing the two feedstocks separately (configuration (4) according to the invention) can significant (more than 10%) energy savings be achieved compared to the reference It is noted that in comparison with the example. A simple reversal of the column (configuration (3)) or a separate introduction of the two feedstocks carried out independently of each other (configuration (2)) also does not make it possible to obtain significant energy savings.

In this example, the choice is made to direct the C6-C7 fraction originating from the aromatics extraction unit (P1) directly to the benzene column (C9), since the benzene column (C9) is connected to the toluene column ( This is the case downstream of C10). This is because its content of C8+ compounds (767 kg/h) is higher than the content of C8+ compounds desired in the bottom product from the toluene column (C10) (267 kg/h).

(Example 2)
The compositions of the two feedstocks in the benzene, toluene, C8+ compound separation section (F) are shown in Table 4.

In this example, due to the content of C8+ compounds in the feedstock (1) (192 kg/h), the aromatics separation unit It becomes possible to direct the feedstock (1) derived from the C6/C7 cut derived from (P1) directly to the benzene column (C9).

Three fractional distillation configurations are evaluated:
- Configuration (1) (corresponds to the reference separation method and device): the benzene column is fed with a mixture of two feedstocks. The bottom of the benzene column is fed to the toluene column.
- Configuration (5) (consistent with the invention): the toluene column is fed only with feedstock (2). Feedstock (1) is mixed at the top of the toluene column. This mixture is fed to a benzene tower.
- Configuration (6) (according to the invention): The toluene column is fed only with feedstock (2). Feed (1) and the top of the toluene column are fed separately to the benzene column.

The fraction leaving the separation section (F) is enriched in benzene, toluene and C8+ compounds and produces products according to the compositions of Table 5 according to configuration (1) and Table 6 according to configurations (5) and (6), respectively. It is.

The content of C8+ compounds in feedstock (1) is the same as in configuration (1) in the toluene-rich product (268 kg/h) in configurations (5) and (6). low enough that it is possible to obtain a content of

The location of the feed is optimized in each of the configurations to minimize the reboiling energy consumption of each of the columns.

The geometry and energy consumption of each of the configurations are shown in Table 7.

Configurations (5) and (6) consistent with the invention are more energy efficient than configuration (1) consistent with the reference separation method and device.

Claims (15)

A method for separating feedstocks comprising benzene, toluene and compounds having 8 or more carbon atoms in a separation device, the separation device comprising at least one reformate column (C1) and at least one reformate column (C1). comprising an aromatic compound extraction unit (P1) and at least one transalkylation unit (P4 ), and from the plurality of units, the aromatic compound extraction unit (P1) and the transalkylation unit (P4). The effluent of is separated in the following distillation columns: benzene column (C9), toluene column (C10) and stabilization column (C11), and the process comprises the following steps:
feeding the toluene column (C10) directly with the C7+ fraction originating from the bottom of the stabilization column (C11) located downstream of the transalkylation unit (P4), enriched in benzene and toluene. and a bottom product from the toluene column (C10) enriched in compounds having 8 or more carbon atoms.
The benzene column (C9) is fed with the top product from the toluene column (C10) and enriched with the benzene-enriched top product from the benzene column (C9) and toluene from the benzene column (C9). and feeding the toluene-enriched bottom product from the benzene column (C9) to the transalkylation unit (P4),
feeding the essentially aromatic fraction originating from the aromatics extraction unit (P1) to the toluene column (C10);
the feeding of the toluene column (C10) originating from the aromatics extraction column (P1) is carried out separately from and above the feeding of the toluene column (C10) originating from the bottom of the stabilization column (C11); or feeding the essentially aromatic fraction originating from the aromatics extraction unit (P1) to the benzene column (C9) as a mixture with the top product from the toluene column (C10) or separately therefrom. how to. 2. The toluene column (C10) is further fed with the top product from the purification column (C6) as a mixture with or separately from the C7+ fraction originating from the bottom of the stabilization column (C11). Separation method as described. 2. The transalkylation unit (P4) is further fed with the top product from the purification column (C6) as a mixture with or separately from the bottom product from the benzene column (C9). Separation method. The separation device further comprises a para-xylene separation unit (P2) and a xylenes isomerization unit (P3), and the effluent is transferred to the following further distillation columns: xylenes column (C2), heavy aromatics column (C3), a raffinate column (C4), an extract column (C5), a purification column (C6), a deheptanization column (C7) and a stripper (C8), according to any one of claims 1 to 3. separation method. 5. Separation process according to claim 4, wherein only the xylenes column (C2) and the heavy aromatics column (C3) feed C9+ aromatics to the transalkylation unit (P4). A reformate column (C1) is fed with a feedstock to produce a C7-cut at the top of the reformate column (C1), and the C7-cut is fed to an aromatics extraction unit (P1). 6. The separation process according to claim 1, wherein the paraffinic compounds are extracted from the C7 fraction and an essentially aromatic fraction is produced. The operating conditions for the benzene tower (C9) are as follows:
Temperature: 130°C to 180°C in the reboiler, 70°C to 130°C in the condenser;
The separation method according to any one of claims 1 to 6, wherein the benzene column (C9) includes 35 to 55 theoretical plates. The operating conditions of the toluene column (C10) are as follows:
Temperature: 130°C to 260°C in the reboiler, 50°C to 200°C in the condenser;
The separation method according to any one of claims 1 to 7, wherein the toluene column (C10) comprises 30 to 55 theoretical plates. Device for the separation of feedstocks containing benzene, toluene and compounds with 8 or more carbon atoms, comprising at least one reformate column (C1) and at least one aromatics extraction unit (P1) and at least one transalkylation unit (P4); The column further includes a benzene column (C9), a toluene column (C10) and a stabilization column (C11),
- the toluene column (C10) is fed with the C7+ fraction originating from the bottom of the stabilization column (C11) located downstream of the transalkylation unit (P4) and is enriched in benzene and toluene; suitable for delivering the top product from (C10) and the bottom product from the toluene column (C10) enriched in compounds having 8 or more carbon atoms;
- The benzene column (C9) is fed with the top product from the toluene column (C10) and receives the benzene-rich top product from the benzene column (C9) and toluene from the benzene column (C9). the transalkylation unit (P4) is suitable for treating the toluene-enriched bottom product from the benzene column (C9);
The toluene column (C10) is suitable for being fed the essentially aromatic fraction originating from the aromatics extraction unit (P1) and toluene originating from the aromatics extraction unit (P1). The feed of the column (C10) is carried out separately from and above the feed of the toluene column (C10), which originates from the bottom of the stabilization column (C11), or the benzene column (C9) is fed with aromatic compounds. A device suitable for feeding the essentially aromatic fraction originating from the extraction unit (P1) as a mixture with or separately from the top product from the toluene column (C10). The toluene column (C10) is suitable for feeding the top product from the purification column (C6) as a mixture with or separately from the C7+ fraction originating from the bottom of the stabilization column (C11). 10. The separation device according to claim 9. The transalkylation unit (P4) is suitable for feeding the top product from the purification column (C6) as a mixture with or separately from the bottom product from the benzene column (C9), as claimed. Separation device according to item 9. a para-xylene separation unit (P2), a xylenes isomerization unit (P3) and the following further columns for the distillation of said effluent: xylenes column (C2), heavy aromatics column (C3), raffinate. Separation device according to any one of claims 9 to 11, further comprising a column (C4), an extract column (C5), a purification column (C6), a deheptanization column (C7) and a stripper (C8). The reformate column (C1) is fed with feedstock and is suitable for producing a C7-fraction at the top of the reformate column (C1), and the aromatics extraction unit (P1) is fed with a feedstock and is suitable for producing a C7-fraction at the top of the reformate column (C1). Separation device according to any one of claims 9 to 12, suitable for extracting paraffinic compounds from a C7-cut and producing an essentially aromatic fraction. . The benzene tower (C9) was operated under the following operating conditions:
Temperature: 130°C to 180°C in the reboiler, 70°C to 130°C in the condenser;
Pressure: 0.1 MPa to 0.5 MPa; and the benzene column (C9) is suitable to be used under comprising 35 to 55 theoretical plates. separation device. The toluene column (C10) was operated under the following operating conditions:
Temperature: 130°C to 260°C in the reboiler, 50°C to 200°C in the condenser;
Separation according to any one of claims 9 to 14, wherein the toluene column (C10) is suitable for use in a pressure: 0.05 MPa to 1 MPa; device.